Thermotropic liquid crystalline polymers (LCPs) have become important items of commerce, being useful as molding resins for general purpose uses, and more specifically in the electrical and electronics industries due to their thermal stability, chemical resistance, and other desirable properties.
For many electrical and electronics applications, LCP molding resins should in particular exhibit properties such as good adhesion and low surface roughness. Such applications include chip carriers, printed circuit boards, integrated circuits, encapsulated chips, and surface mount components, to name a few.
Injection molded specimens and extrudates of LCP compositions consist of skin surfaces, inner skin layers, and unoriented cores. See, e.g., “The Structure of Thermotropic Copolyesters”, Linda C. Sawyer and Michael Jaffe, Journal of Material Science 21, 1897-1913 (1986). The skin surfaces can be separated from the inner skin layers with little force. Thus, in a metallized surface, even though the metal plating can adhere to the skin surface to form a metallized layer, one is still faced with the weak bonding between this metallized layer and the inner skin layers, resulting in failure of the metallized surface under stress. Glass reinforcement has aided greatly in reducing this effect. However, glass fibers give rise to rough surfaces, which are undesirable and unsuitable in most electronic applications.